test: design and implement collaborative DFD editing integration tests

[ericfitz]

Overview

Design and implement integration tests for collaborative (multi-user) DFD diagram editing. This was identified during the comprehensive E2E test planning as an important but independent area that deserves its own design cycle.

Context: The DFD editor supports real-time collaboration via WebSocket — multiple users can edit the same diagram simultaneously. This requires multi-browser-context testing and covers complex scenarios including concurrent edits, conflict resolution, and session management.

Scope (to be designed)

Potential test scenarios to explore during design:

• Two users join the same diagram session
• User A makes a change, User B sees it in real-time
• Concurrent edits to different parts of the diagram
• Concurrent edits to the same element (conflict resolution)
• User disconnect and reconnect
• Session host transfer
• Participant list updates

Why Separate

• High implementation effort (multi-context WebSocket testing)
• Failure modes are often server-side
• Requires careful design around timing, synchronization, and flakiness
• Independent of the other E2E phases

Next Steps

1. Design the test architecture for multi-user WebSocket scenarios
2. Define seed data requirements (shared diagram, multiple users with appropriate permissions)
3. Implement and validate

Related

• Comprehensive E2E test plan: docs/superpowers/specs/2026-04-10-e2e-comprehensive-test-plan-design.md

[ericfitz]

Test coverage analysis (2026-05-15) — relevant findings for this issue

A coverage analysis of tmi-ux (branch dev/1.4.0) surfaced two large gaps that fall squarely within the scope of this issue. Recording them here so they are captured against #581 rather than tracked separately:

DFD infrastructure adapters — the X6 + WebSocket integration layer is entirely unspec'd

No spec files exist for:

• infra-x6-graph.adapter.ts — 2486 lines, 8.9% statement coverage — the master graph adapter.
• infra-dfd-websocket.adapter.ts — 641 lines, no spec.
• infra-websocket-collaboration.adapter.ts — 593 lines, no spec.
• infra-x6-event-handlers.adapter.ts — 388 lines, no spec.
• infra-x6-event-logger.adapter.ts — 501 lines, no spec.
• infra-x6-tooltip.adapter.ts, infra-local-storage.adapter.ts.

The collaborative-editing path (real-time WebSocket sync of diagram operations) has near-zero unit coverage. The collaboration integration tests planned in this issue are the right vehicle to address it.

dfd-collaboration.service.ts — 2131 lines @ 27% coverage

A 550-line spec exists for a 2131-line service. Collaboration session lifecycle, presenter handoff, and participant state are mostly untested. This service should be exercised as part of the collaborative-editing test work.

Related cleanup

• vitest.config.ts excludes infra-x6-graph.adapter.spec.ts — a path that no longer exists (the adapter was renamed). The stale exclude should be removed or replaced with a real spec.
• src/app/pages/dfd/integration/** is excluded from vitest "until migrated to Playwright"; that migration is incomplete, so those styling/cursor/visual-effects assertions currently run nowhere. Worth resolving alongside this work.